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Historic Preservation - Technical Procedures

Spectitle:

Removing Paint From Wrought Iron, Cast Iron And Steel Using Chemical Methods

Procedure code:

0501017R

Source:

Developed For Hspg (Nps - Sero)

Division:

Metals

Section:

Metal Materials

Last Modified:

02/24/2012

Details:

Removing Paint From Wrought Iron, Cast Iron And Steel Using Chemical Methods



REMOVING PAINT FROM WROUGHT IRON, CAST IRON AND STEEL USING
CHEMICAL METHODS


THE CLEANING OR STRIPPING OF METALS MAY INVOLVE THE USE OF
ABRASIVES, LIQUIDS OR SOLVENTS WHICH MAY SPLASH OR RUN OFF ONTO
ADJACENT MATERIALS.  TAKE SPECIAL CARE TO PROTECT ALL ADJACENT
MATERIALS, AND DO NOT USE THIS PROCEDURE ON METALS OTHER THAN
THOSE
SPECIFIED IN THE SUMMARY.

BEFORE UNDERTAKING ANY PROJECT INVOLVING PAINT REMOVAL, APPLICABLE
STATE AND FEDERAL LAWS ON LEAD PAINT ABATEMENT AND DISPOSAL MUST
BE
TAKEN INTO ACCOUNT AND CAREFULLY FOLLOWED.  STATE AND FEDERAL
REQUIREMENTS MAY AFFECT OPTIONS AVAILABLE TO OWNERS ON BOTH PAINT
REMOVAL AND REPAINTING.  THESE LAWS, AS WELL AS ANY REQUIREMENTS
PROHIBITING VOLATILE ORGANIC COMPOUNDS (VOCs), SHOULD BE REQUESTED
FROM THE STATE HISTORIC PRESERVATION OFFICER IN EACH STATE.  (From
Preservation Brief 28, "Painting Historic Interiors".)  REGULATORY
INFORMATION MAY ALSO BE REQUESTED FROM THE ENVIRONMENTAL
PROTECTION
AGENCY (EPA) REGIONAL OFFICE AND/OR THE STATE OFFICE OF
ENVIRONMENTAL QUALITY.


PART 1---GENERAL

1.01 SUMMARY

    A.   This procedure includes guidance on chemically removing
         paint from wrought iron, cast iron and steel.  These
         metals should be repainted immediately following paint
         removal in order to prevent exposure to the atmosphere
         and subsequent corrosion.

    B.   For information on painting and coating these materials
         see 05010-13-S "Primers and Paints for Wrought Iron, Cast
         Iron and Steel", 05010-18-R "Applying a Sacrificial
         Coating to Wrought Iron, Cast Iron and Steel", and
         09900-07-S "General Guidelines for Painting Exterior and
         Interior Surfaces".

    C.   Chemical methods as used herein shall apply to the use of
         commercial chemical paint strippers and rust removers.

    D.   There are several causes for paint failure on metal.
         Excess moisture can cause rusting.  As metal rusts, the
         rust expands breaking the bond between the metal and the
         paint.  Inadequate or improper surface preparation can
         interfere with the proper bonding of the new paint.  The
         wrong primer can cause anything from pitting of the metal
         surface to peeling of the new paint.

    E.   It is not necessary to remove all previous coats of paint
         if:

         1.   they are adhering soundly,

         2.   the new painting system is compatible,

         3.   important design details are not being obscured by
              the paint layers.

    F.   An archives of the paint history of the building is to be
         maintained.  This is to include the paint samples taken
         during research, samples of the new paint colors and the
         manufacturers technical information.

    G.   Safety Precautions:

         1.   No food or drink shall be allowed near any work
              station so as to prevent contamination from paint,
              paint chips or paint dust which may contain lead
              and other toxic substances.

         2.   Paint being removed most likely will contain lead.
              All workmen must wear protective clothing,
              (including hair), goggles and respirators with
              proper filters.

         3.   Protective clothing shall be removed at the end of
              each day and kept at the site to prevent workers
              from taking dust and paint chips to other parts of
              the site or to their homes.

         4.   Wash hands and face often, especially before eating
              and at the end of the day.

         5.   All waste material shall be collected at the end of
              each work day and disposed of in a manner
              consistent with local environmental regulations.
              It is considered Hazardous Waste.

         6.   Work area shall be sealed to prevent the spread of
              paint dust and debris beyond the work site.

         7.   After paint removal is complete, all areas around
              the building shall be cleaned of all paint dust and
              debris, and such debris shall be properly disposed
              of in a manner consistent with local environmental
              regulations.

    H.   See 01100-07-S for general project guidelines to be
         reviewed along with this procedure.  These guidelines
         cover the following sections:

         1.   Safety Precautions

         2.   Historic Structures Precautions

         3.   Submittals

         4.   Quality Assurance

         5.   Delivery, Storage and Handling

         6.   Project/Site Conditions

         7.   Sequencing and Scheduling

         8.   General Protection (Surface and Surrounding)

         These guidelines should be reviewed prior to performing
         this procedure and should be followed, when applicable,
         along with recommendations from the Regional Historic
         Preservation Officer (RHPO).

    I.   For additional information on cast and wrought iron see
         the following HBPP procedures:

         1.   05010-04-S, "Cast Iron:  Characteristics, Uses and
              Problems."

         2.   05010-11-S, "Wrought Iron:  Characteristics, Uses
              and Problems."

         3.   05010-01-S, "Checklist for Inspecting Cast Iron
              Failures."


PART 2---PRODUCTS

2.01 MANUFACTURERS

    A.   For Chemical Paint Removers:

         1.   ProSoCo, Inc.
              755 Minnesota Avenue
              P.O. Box 1578
              Kansas City,  KS  66117
              800/255-4255 or 913/281-2700

              Availability:  Through contractors licensed by
              manufacturer.

         2.   Star Bronze Co.
              P.O. Box 2206
              Alliance, OH  44601
              216/823-1550

         3.   Savogran Company
              P.O. Box 130
              Norwood, MA  02062
              800/225-9872 or 617/762-5400

2.02 MATERIALS

    NOTE:  Chemical products are sometimes sold under a common
    name.  This usually means that the substance is not as pure as
    the same chemical sold under its chemical name.  The grade of
    purity of common name substances, however, is usually adequate
    for stain removal work, and these products should be purchased
    when available, as they tend to be less expensive.  Common
    names are indicated below by an asterisk (*).

    A.   Chemical Paint/Lacquer Removers:

         1.   Manufacturer's standard thixotropic/alkaline
              formulation for removing paint coatings from
              ornamental metal work, such as "Sure Klean 509
              Paint Stripper" (ProSoCo, Inc.), or approved equal.

         2.   Semi-paste, water rinsing, nonbenzol remover such
              as "Strypeeze Semi-Paste" (Savogran Company), or
              approved equal.

              a.   Characteristic orange color.  

              b.   Will work on both latex and oil-based paints,
                   lacquers and varnishes.  

              c.   Cling well to round or vertical surfaces.  

              d.   Form an anti-evaporative film as they dry.  

              e.   Clean-up by either washing or scraping off.
                   All traces must be removed and a neutral pH
                   achieved before repainting.

         3.   Non-flammable, heavy bodied, methylene-chloride
              based remover such as "Super Strip Non-flammable",
              "Zip-Strip" (Star Bronze Co.), or approved equal.

              a.   Good for interior use because they are non-flammable.  

              b.   Will soften oil-based paints, lacquers,
                   varnish and synthetic baked finishes.  

              c.   Because they are so heavy bodied they will
                   cling to vertical and irregular surfaces.  

         4.   Non-flammable, water rinsing, liquid remover such
              as "H2O Off", or approved equal:  Available from
              paint supply store.

              a.   Often methylene-chloride based.  

              b.   Will soften oil-base paints, varnish, and
                   synthetic baked finishes.  

              c.   Will not work on vertical surfaces.  Good for
                   horizontal surfaces.

         5.   Liquid benzol remover such as "Kutzit", or approved
              equal:  Available from paint supply store.

              a.   HIGHLY FLAMMABLE, HIGHLY TOXIC.  WEAR
                   PROTECTIVE CLOTHING, USE IN WELL VENTILATED
                   AREA, DO NOT USE NEAR FLAME, SPARKS, OR
                   HEATER.  

              b.   Will remove oil-based paint, lacquer. varnish
                   and synthetic baked finishes.  

              c.   Work well on flat surfaces.  Work quickly.  

    B.   Chemical rust removers, such as "Navel Jelly", or
         approved equal.

    C.   Cornstarch or fumed silica to further thicken chemicals
         so they will adhere to vertical surfaces.

    D.   Liquid Strippable Masking Agent:  Manufacturer's standard
         liquid, film forming, strippable masking material for
         protecting glass, and polished stone surfaces from
         damaging effect of acidic and alkaline cleaners, such as
         "Sure Klean Acid Stop" (ProSoCo, Inc.), or approved
         equal.

    E.   Mineral Spirits:  (To remove chemical residue)

         1.   A petroleum distillate that is used especially as a
              paint or varnish thinner.

         2.   Other chemical or common names include Benzine*
              (not Benzene); Naphtha*; Petroleum spirits*;
              Solvent naphtha*.

         3.   Potential Hazards:  TOXIC AND FLAMMABLE.

         4.   Safety Precautions:

              a.   AVOID REPEATED OR PROLONGED SKIN CONTACT.

              b.   ALWAYS wear rubber gloves when handling
                   mineral spirits.

              c.   If any chemical is splashed onto the skin,
                   wash immediately with soap and water.

         5.   Available from construction specialties
              distributor, hardware store, paint store, or
              printer's supply distributor.

    F.   Phenolphthalein:  Used to test pH of a surface after
         stripping with chemicals or any alkaline product.
         Available at some drug stores or chemical supply houses.

    G.   Trisodium Phosphate:

         NOTE:  THIS CHEMICAL IS BANNED IN SOME STATES SUCH AS
         CALIFORNIA.  REGULATORY INFORMATION AS WELL AS
         ALTERNATIVE OR EQUIVALENT CHEMICALS MAY BE REQUESTED FROM
         THE ENVIRONMENTAL PROTECTION AGENCY (EPA) REGIONAL OFFICE
         AND/OR THE STATE OFFICE OF ENVIRONMENTAL QUALITY.

         1.   Strong base-type powdered cleaning material sold
              under brand names.

         2.   Other chemical or common names include Sodium
              orthophosphate; Tribasic sodium phosphate;
              Trisodium orthophosphate; TSP*; Phosphate of soda*.

         3.   Potential Hazards:  CORROSIVE TO SKIN.

         4.   Available from chemical supply house, grocery store
              or supermarket, hardware store or paint store.

    H.   Soft cloths

    I.   Steel wool

    J.   Plastic sheeting and duct tape to cover the stripper
         during dwell time.

2.02 EQUIPMENT

    A.   000 steel wool or synthetic pads

    B.   Scrapers and small picks to remove sludge

    C.   Steel or brass wire brushes

    D.   Fiber bristle brushes (1/2 to 3/4 inches long)

    E.   Metal containers such as old coffee cans in which to
         dispose of sludge


PART 3---EXECUTION

3.01 EXAMINATION

    A.   Before work is begun on removing the existing paint film
         or otherwise preparing the surface all sources of excess
         moisture shall be inspected and repaired or replaced as
         required.  

3.02 PREPARATION

    A.   Protection:

         1.   Comply with recommendations of manufacturers of
              chemical cleaners for protecting building surfaces
              from exposure to their products.

         2.   Protect glass, unpainted metal trim and polished
              stone from contact with acidic chemical cleaners by
              covering them with liquid strippable masking agent
              or polyethylene film and waterproof masking tape.
              Apply masking agent to comply with manufacturer's
              recommendations.  Do not apply liquid masking agent
              to painted or porous surfaces.

         3.   Protect unpainted metal from contact with alkali
              chemical cleaners by covering them either with
              liquid strippable masking agent or polyethylene
              film and waterproof masking tape.

         4.   Protect adjacent surfaces, including grass, shrubs
              and trees with paper, drop cloths and other means.
              Items not to be painted which are in contact with
              or adjacent to painted surfaces shall be removed or
              protected prior to surface preparation and painting
              operations.

         5.   All waste material shall be collected at the end of
              each work day and properly disposed of.  It is
              considered Hazardous Waste.

         6.   Work area shall be sealed to prevent the spread of
              dust and debris beyond the work site.

         7.   If vacuums are used to clean area, machines shall
              be equipped with HEPA (High Efficiency Particulate
              Air) filters to insure all lead dust has been
              contained and removed.

3.03 ERECTION, INSTALLATION, APPLICATION

    A.   Rust Removal:

         1.   Brush apply commercially available chemical rust
              removers such as "Naval Jelly" (phosphoric acid),
              and allow to dwell according to manufacturer's
              instructions.

              CAUTION:  STAY AWAY FROM HYDROCHLORIC ACID BASED
              PRODUCTS AS THEY MAY LEAD TO FUTURE CORROSION.

         2.   Wipe off residue with mineral spirits and either
              steel wool or soft rags.

         3.   Dry immediately with clean soft cloths or using an
              industrial blow dryer.  Follow direction of grain
              in metal.  DO NOT TOUCH CLEANED ORNAMENTAL METAL
              SURFACE.

         4.   Prime immediately to prevent rust.  

    B.   Clean small pieces which can be removed.

         NOTE:  REMOVE ONLY AS MUCH PAINT AND RUST EACH DAY AS CAN
         BE PRIMED THAT SAME DAY.  BARE IRON AND STEEL WILL BEGIN
         TO RUST AGAIN WITHIN A MATTER OF HOURS.  IT SHOULD NOT BE
         ALLOWED TO SIT UNPROTECTED OVERNIGHT.

         1.   Soak in a solution of hot water and TSP or sudsy
              ammonia to loosen the paint.

         2.   Remove paint with scrapers and/or a wire brush.  

         3.   A final wipe down with mineral spirits may be
              necessary to help remove final traces of paint.

         4.   Dry immediately and prime to prevent rusting.  A
              heat gun, set at the lowest temperature, can be
              used to hasten the drying time.  DO NOT USE HIGH
              HEAT AS THIS MAY DISTORT THE METAL MEMBERS.  

    C.   Remove any loose paint not already removed with the rust
         using a chemical paint remover.  

         NOTE:  IF THE PAINT IS ADHERING SOUNDLY LEAVE IT ALONE-IT
         PROVIDES EXTRA PROTECTION.  FEATHER THE EDGES OF THESE
         AREAS TO PROVIDE A SMOOTH FINISH AND APPEARANCE.

         1.   Brush the chemical onto the surface in the amount
              recommended by the manufacturer.  Thicken if
              necessary with cornstarch or fumed silica.  

         2.   Cover with plastic and allow to sit or "dwell"
              according to the manufacturer's instructions.  

         3.   Remove sludge using scrappers and steel wool.  A
              second application may be required on those areas
              where paint is especially thick or the detail is
              intricate.

         4.   After removal has been completed using chemicals
              rub all surfaces down with mineral spirits to
              remove all traces of chemical and waxy residue.

              a.   To test whether all chemicals have been
                   removed and a neutral pH achieved, dissolve a
                   2" piece of phenolphthalein in denatured
                   alcohol.  

              b.   Brush the solution onto the surface.  If it
                   turns a shade from pink to magenta there is
                   still chemical residue.  

              c.   Treat the surface with additional mineral
                   spirits and continue testing until there is no
                   color change in the phenolphthalein solution.

         5.   Dry thoroughly and prime immediately to prevent
              rust.  

    D.   Paint all surfaces.  For guidance see 05010-13-S "Primers
         and Paints for Wrought Iron, Cast Iron and Steel",
         05010-18-R "Applying a Sacrificial Coating to Wrought
         Iron, Cast Iron and Steel", and 09900-07-S "General
         Guidelines for Painting Exterior and Interior Surfaces".

                         END OF SECTION